Process of producing wood pulp



June 1 1, 1929. SCHQUTEN 1,717,266

PROCESS OF PRODUC-ING WOOD PULP Filed March 2, 1927 l I H m P llg m "W""I I v I I nvenlonv 7141s zl'lbrne q. f

. Patented June 11, 1929.

UNITED STATES 1,717,266 PATENT OFFICE.

FRANS KAREL LOUIS SCHOUTEN, OF ZAANDAM, NETHERLANDS.

PROCESS OF PRODUCING WOOD PULP.

Application filed March 2, 1927, Serial No. 172,045, and in GermanyMarch 5, 1926.

The invention relates to the manufacture of I wood pulp from logs orfrom wood Waste, its

object being to produce, by a mechanical process, pulp approximating inquality to hot ground.

According to my process the comminuted raw material, with its naturalcontent of moisture, or moistened to restore the normal moisturecontent, is first subjected to so-called dry refining, and is thensubjected to further refining (wet refining) in the presence of anappropriate proportion of added water.

-This process has the advantage of producing the operation beingcontinued till as far as convenient or practicable even the smallestbundles are divided into separate fibres. This may be done in threestages, to wit First stage.The raw material, holding its naturalmoisture content, is cut up or otherwise comminuted. 3'0

Second stage.-The coniminuted material, still holding itsnaturalmoisture content, is subjected to dry refining.

Third stage.-In order finally to separate the fibres the material issubjected to Wet refining, in the form of a thick pulp.

Logs, boards,.wood-shaving and so on may all be used as raw materials.

Such material may for the purposes of the process first be cut up intosmall slabs or wafers, which are then divided longitudinally of thefibres, the broken fibres and sawdust being separated, which may be doneby any method usually adopted for that purpose, for example inElfjSCIGGII. 'Thereupon the fine woodflour, sawdust, sand and otherimpurities may be removed by sifting. Thereupon follows the alreadymentioned first refining process, namely a dry process, in which thewood holds only its natural moisture content,

ture may be introduced to restore the normal content, so that themechanical treatment in the so-called dry refining process does notunduly tear the fibres.

The dry refining preceding the wet refining has the efiect of dividingup the wood into bundles of fibres of fairly uniform size.

It is desirable for the purposes of the invention artificially toincrease the heat produced by friction in the course of the dry refiningprocess. For this purpose we may, for example, subject the beaters orcoacting members of the refining apparatus to the action of springs orweights whereby their surfaces are pressed towards each other. The heatdue to the resulting increased friction generates vapour in the Wood,which opens up the cells. When the wood cells, thus loosened, are placedin the apparatus for wet refining, which imparts to the material thegeneral characteristics of hot ground, the treatment produces apulp'capable of being inade into paper with very closely felted fibreayers.

The treatment in the Wet refiner disintegrates practically all the wood,even the smallest portions introduced into that apparatus, so that eventhese small bundles of fibres are opened up and converted into a loosefibrous state, as in hot ground. For this purpose the material on itsway from the dry refiner to the wet refiner must be made into a pulp ofsuch stiffness that its temperature is increased by friction in the wetrefiner.

This pulp may be produced in a vat, which is interposed between the'dryand wet refiners, and from which the pulp is conveyed to the wet refinerby means of a suitable conveyor.

The thick pulp leaving the wet refiner may receive an addition of water,and then pass on to a sorting apparatus, wherein such bundles of fibresas have not been fully disintegrated or shredded are separated, in orderto pass back to the vat and be mixed with the fresh material coming fromthe dry refiner. This prevents or reduces the occurrence of waste in thefinal stage of the process. The amount of water added to the materialcoming from the dry refiner is, of course, regulated with due regard tothe water brought with the pulp which is returned to the'vat afterpassing through the wet refiner and sorter. The water flowing from thesorting apparatus may, in fact, be used for regulating the consistencyof the pulp which is sup plied to the wet refiner.

are further divided. From the machines 2,

the material passes to a sifting machine 3, wherein broken fibres andlike waste material, sand and other impurities are separated. Thistreatment completes the first stage.

For the second stage of the process the material passes into the dryrefiner 6, where the pieces of wood are divided up into coarse bundlesof fibres, by being split longitudinally, heat being artificiallygenerated by* friction during this treatment.

If the material coming from the sifter is too dry for this treatment itis first conveyed from the sifter to a chamber 5, wherein it is treatedwith water from a container 4, to restore the natural moisture contentof the wood, whereupon it passes into the dry refiner 6, in which thesecond stage of the process is completed.

For the third stage the small bundles or bunches of fibre produced inthe dry refiner 6 are passed to vat 7, in order to convert into a pulpof the consistency suitable for wet refining. A pump 8 or equivalentapparatus delivers this pulp to the wet refiner 9, in which thetreatment, in so far as is practicable, is accompanied by artificialgeneration of heat by friction.

The fpulp from the wet refiner, with addition 0 an appropriate quantityof water, passes to the sorting or straining apparatus 10, where anycoarse material left in the pulp is separated. The strained pulp passeson to the drier 11, and the water containing the Presses, centrifugalapparatus or the like I may be used for further separation of water fromthe pulp, and putting it into packet form. A press for this purpose isshown at 12. From such a press the material can be taken in a form readyfor the market, with a moisture content of only 50 to 55%.

Alternatively the pulp coming from the sorter or strainer can bethickened to the consistency suitable for treatment in a beater, andused for paper making, the treatment in the drier 11 and press 12 beingdispensed with.

l/Vhat I claim is:

The process of mechanically producing wood pulp comprising mechanicallycominuting the raw material, dry refining it with suflicient friction tovaporize its normal water content, and wet refining it in mixture withIn testimony whereof I have aflixed my signature.

FRANS KAREL LOUIS SCHOUTEN.

